Liners for sealing caps have been commonly used in the past, where the sealing cap is used on a bottle or other like container having an opening and said cap is securable to the bottle or container for enclosing the opening. Liners are relatively well known and are designed essentially to maintain a seal between the container finish land lip and the surface of the liner overlying the same, wherein said liner is placed between the sealing cap and the container. A fluid-impervious seal at the container finish land is highly desirable to prevent permeation or leakage of fluids from the container into or out of said container. These terms refer to the passage of fluid through the gap between a barrier and object such as the cap liner and the bottle or other container.
A major problem arises when the container is packaged with a product which evolves a gas or is under pressure, which pressure might increase excessively under certain conditions, such as elevated temperature and/or change in atmospheric pressure. It is desirable for the seal to be semi-permeable to the gas and permit excessive internal pressure to vent to the atmosphere, while retaining the associated liquid within the container. Thus, the breakage of the closure or the container is precluded by the release of excessive internal pressure.
Previous conventional cap liners have included one-piece or multi-layered liners constructed of materials such as corrugated fiber board, paper board, plastic, foil or the like, and may also include a coating on one or both major surfaces that is resistant to fluid permeation. Such designs, although relatively inexpensive and effective in precluding permeation, or leakage of fluids from the bottle or container, do not allow for pressure equilibration caused by liquids which off-gas or changes in external ambient pressure.
To address the above problems, venting liners have been used.
A major problem of conventional venting liners is their inability to vent with consistency at a particular pressure or a limited range of internal and external pressures within an associated container. Also perceived as a problem with conventional venting liners is their inability to reversibly vent only the gaseous portion, whereby equilibrated pressure can be maintained within the container with respect to the relatively increased external pressure.
Cap liners have been constructed of synthetic materials such as thermoplastics. U.S. Pat. No. 4,121,728, entitled "Venting Liners" shows one such cap liner having a first ply constructed of an impermeable plastic and a second ply constructed of a foamed material that is compressibly deformable. Both plies are simultaneously extruded and laminated together to form the cap liner. The first ply of the cap liner is applied to the bottle or container as the cap is secured to the container. The second ply is compressed between the bottle and the cap and urges the first ply into a sealing contact with the bottle or container.
Other examples of venting structures for relieving excessive pressure build up in a container include U.S. Pat. No. 2,424,801, which discloses one type of venting structure wherein the glassware neck is provided with a special configuration which will permit gas to escape after the gas build-up has reached a point where it will lift the liner off the neck of the glassware.
U.S. Pat. No. 3,114,467 discloses another type of seal-venting bottle cap wherein the bottle cap is provided with a special structure which permits the liner to rise up under the action of the build-up of gas pressure, the raising of the liner away from the neck of the glassware, then permits the gas to escape. These structures have the disadvantageous deficiency, while permitting gas to escape, they are also equally suitable for permitting liquid to escape. Neither '801 or '467 provide for or contemplate the possibility of pressure equalization, i.e., reverse flow of gas to equilibrate the pressure in the container with atmospheric pressure.
U.S. Pat. No. 3,448,882 relates to a liner composed of a pulpboard backing with a facing of fibrous, semi-permeable, polytetrafluoroethylene which permits the passage of gasses but is not wetted by and prevents the passage of liquid from within the container.
In many instances, while various structures and liners for sealing bottles or containers are available, they all suffer from major deficiencies. While the structures will permit gas to escape, they are not all equally suitable for preventing liquid from escaping. In some cases escaping liquid can damage the material for one or more portions of the liner structure.
Although cap liners such as U.S. Pat. Nos. 4,121,728 and 4,789,074 are more effective than cardboard or pulpboard cap liners against fluid permeation or leakage, such cap liners inherently require relatively expensive materials and manufacturing techniques. For example, the second ply in the '728 patent provides an imperfect and co-extensive layer of deformable material, even though only a relatively small portion of the second ply is actually compressed between the sealing lip of the bottle and the cap. The remainder of the second ply is not required to mechanically reinforce the first ply, therefore the non-essential material in the second ply represents an unnecessary expense.
U.S. Pat. No. 4,789,074 discloses a cap liner comprising a first substantial fluid-impervious film, a second compressible resilient "foraminous" reinforcing web bonded to the first film, whereby when the cap closure is secured to the bottle, it must compress the foraminous web between the bottle and the cap resiliently urging the film into sealing contact therewith. In the invention of '074 the foraminous web acts as a spring to force the film, or fronting, into sealing engagement with the top of the bottle finish. Therefore, the web in the '074 patent must resiliently urge the film, or fronting, into sealing contact by a compressive force necessarily exerted thereby during the closure sealing process by the torque provided by the interaction of the threaded bottle cap with the threaded top of the bottle.
U.S. Pat. No. 3,071,276 utilizes a porous paper backing while U.S. Pat. No. 4,789,074 (Han) utilizes a cap liner of a first substantially fluid impervious film and a second compressible resilient foraminous reinforcing web bonded to the first film where the cap closure is secured to the bottle wherein it must compress the foraminous web between the bottle and the cap resiliently urging the film into the sealing contact.
This reference, U.S. Pat. No. 4,121,728 described above, while having grooves thereon, appears to have several variations from the instant invention. The sealing liner in '728 does not appear to off-gas through to the bottom of the inside or lower panel to the top of the second ply of the closure and then to the sides of the closure. In '728, the sealing liner inside panel and the sides of the closure are meant to deform and retract the sealing means by the pressure of built-up gases in the sealed container, such that by defacing the lower ply, it is lifted up, forming a vent channel and then off-gassing to the sides of the closure. This type of off-gasing can result in fluid leakage if the package is tipped. Utilizing a porous backing, such as disclosed in U.S. Pat. No. 3,071,276 (Pellet) or U.S. Pat. No. 3,448,882, each of which utilizes a pulpboard or porous paperboard backing with a microporous plastic facing are unacceptable as sealing backing for sealing closures because of chemical compatibility with aggressive materials, such as hypochlorite. Also these liners are not effective at allowing gas into the container to equilibrate external pressure increases.
With reference to U.S. Pat. Nos. 4,121,728 and 3,045,854 (Patton), although each of these contains grooves or channels extending laterally across the side surface of the disk, they do not incorporate a porous backing which is semi-permeable and which allows the gases to vent therethrough to channeling which exists on the upper surface of the laminated disk whereby the gases are permitted to off-gas through the sides of the closure.
In view of the foregoing, it is a primary object of the present invention to eliminate the disadvantages heretofore noted by providing a novel venting liner which vents under any closure applied torque, while at the same time being capable of utilization of a non-venting liner.
The primary object of this invention is to provide a novel bi-directional venting liner for closures which includes a shaped member congruent with the container opening defined by at least two plies or layers of material which may or may not be deformable when subjected to a compressive force and wherein grooves or channels are provided on the lower surface of the top layer, although subjected to compressive force, are not compressed. Off-gassing built-up gases from the enclosed container to the atmosphere is by a mechanism whereby the gases are passed directly to the lower surface of the top layer, beneath the closure, the gases travel along the associated channels to the inside of the closure, and then escape to the atmosphere by way of openings existing between the closure and the container neck, for example, the spiral screw threads of the closure and threads of the container neck which in effect forms a continuous channel for the escaping gas. A reverse mechanism is contemplated for the equilibration of pressures when the pressure in the container is less than the external ambient atmospheric pressure with the entering air to the continuous channel between the cap threads and the container neck thereunder.